As the capacity of the lithium ion battery increases, its specific capacity is increasingly high, thus the battery generates more heat during the process of charge and discharge. Accordingly, it is required for the battery itself that the heat generated in the inside of the battery can be dispersed in time. However, the currently used shell of the lithium ion battery is usually in the form of cylinder or square with a relatively small surface area for dispersing the heat, such that during the process of charge, especially in the case of overcharge, the rate of heat-dispersing is far lower than that of heat-generating, resulting that the inner temperature of the battery sharply increases, the stabilities of the electrolyte solution, electrode active materials and binders become poor, the performance of the battery worsens, and the safety problems such as the explosion and fire may even occur.
Because the lithium ion battery possesses a relatively high inner resistance compared with the other secondary batteries, the voltage sharply decreases, the discharge time is greatly shortened, and the capacity is significantly lowered during the process of discharge at large current. The low conductivity of the conventional electrode is one of the main reasons for the lithium ion battery possessing a relatively high inner resistance. Until now, in most commercial lithium ion batteries one single electrode tab (also known as an electrode terminal) is used to conduct the current, which makes the current conducted only at several limited welding points. As a result, the conductivity is low and the distribution of the current is not uniform during the process of charge and discharge.
In addition, the electrode core of the battery of the prior art is usually one single electrode core with a structure of winding or piling-up. However, in the preparation of the battery with a high capacity and high power, the single electrode core with a structure of winding has the disadvantages that the electrode plate is long and difficult to prepare and wind, while the single electrode core with a structure of piling-up has the disadvantages that the practical process is complicate, the electrode plate is difficult to prepare and pile up, and the yield of the eligible products is low.
To sum up, it is very important for the improvement of performances of the power type lithium ion battery to effectively increase the heat-dispersing area of the lithium ion battery to improve the heat dispersion and the safety of the battery, to lower the inner resistance and improve the discharge performance with a high current of the battery, and to increase the yield of the eligible products and reduce the cost.